Specified position identifying method and specified position measuring apparatus

ABSTRACT

A specified position in an array structure in which a reference pattern is displayed repetitively through reference pattern counting is identified. In an array structure image, the pattern detection estimating area generated from a starting point, the address of the starting point, and a unit vector are compared with a pattern detected position found in pattern matching with the reference pattern image, to execute pattern counting while determining correct detection, oversights, wrong detection, etc. Array structure images are photographed sequentially while moving the visual field with the use of an image shifting deflector to continue the pattern counting started at the starting point to identify the ending point specified with an address. If the ending point is not reached only with use of the image shifting deflector, the visual field moving range of the image shifting deflector is moved with use of a specimen stage.

CLAIM OF PRIORITY

The present application claims priority from Japanese application JP2006-086857 filed on Mar. 28, 2006, the content of which is herebyincorporated by reference into this application.

FIELD OF THE INVENTION

The present invention relates to a technique for searching a patterncorresponding to a specified address in a charged particle apparatuswith respect to a specimen having a structure in which similar patternsare disposed repetitively.

BACKGROUND OF THE INVENTION

What is important in semiconductor device manufacturing processes is atechnique for detecting non-confirming or defective articles insemiconductor devices and analyzes the causes. There are some inspectionapparatuses used for detecting such defects; for example, inspectionapparatuses for electrical characteristics of circuits, external viewchecking apparatuses for inspecting foreign matters existing in wiringpatterns, improper shapes of wiring patterns, etc. In those inspectionapparatuses, defects to be subjected to defect cause analysis are pickedup first, then positional information of each specified defect on thesubject specimen is sent to an analyzer, in which electricalcharacteristics, compositions, and cross sectional shapes of thespecified defect are observed.

Usually, the position setting accuracy of a specimen stage used for eachof such inspection apparatuses is several micrometers. In recent years,wiring patterns of semiconductor devices are formed very finely. Forexample, the size of a memory cell block of a memory devicemass-produced in these days is about several hundreds of nanometers.Consequently, it is difficult to report coordinate information of adefect detected in an inspection apparatus to another with requiredaccuracy only with the positional control information of the specimenstage of the inspection apparatus.

Each of wiring patterns and circuit patterns in many semiconductordevices has an array structure in which similarly structured cells aredisposed regularly according to their design data. The design data canbe used as CAD data in various measuring and inspection apparatuses. Incase where a defect detected in an inspection apparatus is to beanalyzed in any of various other analyzing apparatuses, in addition tothe coordinate information of the defect obtained in the inspectionapparatus, the information of the defect position on the design data isalso obtained from the CAD data. Each of the analyzing apparatusesselects an appropriate reference position as a starting point on thesubject specimen and executes matching with the reference position toknow where is the reference position on the CAD data and how far thetarget position of the analysis is away from the reference position.Such a reference position is selected from, for example, an edge of anarray structure of a semiconductor device. At this time, the analyzercounts the number of cells from a given starting point to an endingpoint up to reach the ending point. And pattern measurement (cellcounting) is needed at this time to measure how often a predeterminedpattern appears between the starting point and the ending point. In casewhere the number of patterns is comparatively less, the operator cancount the number of patterns at a visual check. In the case of a devicehaving several hundreds or several thousands of cells, it is stronglyrequired to make pattern counting automatically.

JP-A No. 92883/10 discloses a technique for obtaining an image of atarget position with use of an optical photograph, an electronmicroscope, or the like to count the number of memory cells on a memoryLSI from changes of the brightness or luminosity of the image with useof a pattern recognition device. The pattern recognition device holdsthe ending point of cell counting as a physical address and ends thememory cell counting when the number of counted memory cells matcheswith the value indicated in the physical address. The patternrecognition device determines the counting ended position as a logicaladdress, which is coordinates on the design plan of the memory LSI.

JP-A No. 251824/2000 discloses an invention in which the visual field ofa SEM image is moved while stage moving vectors are detected in a rangefrom a starting point of cell counting to a target point. When the stagemoving distance reaches a predetermined electron beam deflection limit,the stage is stopped once. Then, the number of cells disposed in thevisual field of the observation is extracted at that position. Andaccording to the extracted data, a mutual positional relationshipbetween a disposed cell and another is identified and the visual fieldof the SEM image is moved again. By repeating such movements in manysteps, the specified cell is moved in the visual field of the SEM image.A specimen stage moving vector is obtained by specifying a cell as anindex basic pattern and from a relative movement of the index basicpattern in the visual field of the SEM image before and after thespecimen stage movement. The relative movement of the index basicpattern in the visual field of the SEM image is obtained from adifferential image of the SEM images before and after the specimen stagemovement.

[Patent document 1] JP-A No. 092883/10 [Patent document 2] JP-A No.251824/2000 SUMMARY OF THE INVENTION

Hereunder, a description will be made for problems of conventional cellcounting with reference to FIG. 1. FIG. 1 shows an explanatory diagramfor an image of a semiconductor device observed through a microscope. Onthe semiconductor device are disposed a plurality of plugs regularly.Each circle denotes a plug. In the case of the conventional cellcounting, pattern matching is executed while moving a proper referencepattern 100 at given pitches in the whole area enclosed by edges 101 and102 of an area in which cell counting is made. The number of areasmatching with the reference pattern is counted in the cell counting. Itis premised that the cells to be counted are disposed like a matrix whenin setting a reference pattern.

Actually however, memory cells are not always disposed like a squarematrix; cells are often disposed in a complicated pattern. For example,they might be disposed obliquely and a plurality of patterns might bedisposed in a nested structure. If cell counting is made for such acomplicated pattern with any of the conventional cell counting and bitcounting techniques, the pattern matching becomes complicated and thecomputer used for such cell counting or bit counting comes to be muchloaded. This has been a problem. And in the case of the conventionalcell counting, pattern matching must be done in the whole area thatincludes both starting and ending points. And if the starting and endingpoints are far separated from each other, the number of cells to becounted increases, thereby the computer load increases after all.

Under such circumstances, it is an object of the present invention tosolve those conventional problems by employing a concept of unit vectorwhen in cell counting/bit counting and enabling the pattern repeatingunit to be set freely according to the specimen to be subjected tocell/bit counting. The “unit vector” mentioned here is a specified unitof a coordinate system for representing addresses of both starting andending points when in cell counting. The unit vector has a size and adirection. That is why it is referred to as a unit vector in thisspecification. Hereunder, the unit vector will be described withreference to FIG. 2.

FIG. 2 is an expanded explanatory diagram of part of a semiconductordevice plug formed plane. Each circle denotes a plug. The (a, b) denotesa unit vector, which is assumed as a repeating unit when in cellcounting.

If a unit vector is changed, the address of the cell represented as theunit vector is also changed. For example, if a unit vector is selectedas (a, b) shown in FIG. 2A, the ending point address is represented as(4, 3). Here, the positive/negative of the coordinate axis is defined sothat the directions of the arrows a and b are positive and the oppositedirections of those arrows are negative. On the other hand, if a unitvector is selected as shown in FIG. 2B, the ending point is representedas (4, 6).

In the case of the present invention, a detection estimating area is setaccording to such a unit vector. A detection estimating area means anarea in which a target pattern is expected to exist. A detectionestimating area is set as an area of which center is separated by aninteger multiple of a unit vector from the starting point. Eachdetection estimating area is given an address corresponding to aninteger multiple of the unit vector. A pattern detected in such adetection estimating area is determined as a cell in the address.

If a pattern is detected in a detection estimating area, it is referredto as correct detection. If a pattern is detected outside a detectionestimating area is referred to as wrong detection. If no pattern isdetected in a detection estimating area, it is referred to as anoversight. Information of those positions is recorded. Positioninformation of both recorded wrong detection and an oversight isanalyzed to correct an error occurred when in pattern matching.

Because the concept of the unit vector is employed when in cellcounting/bit counting and the apparatus user can set a pattern repeatingunit freely as described above, the following effects are available. Oneof the effects is reduction of the cell counting/bit counting time.Pattern matching executed only in a detection estimating area can reducethe pattern matching time much more than pattern matching executed inthe whole area between starting and ending points. Furthermore, becausepattern matching is done only in a detection estimating area overlappingwith an additional line shown in FIG. 2 without detecting all the cells,the pattern matching time can be reduced much more. The other of theeffects is that a pattern matching result determination function can beadded to the apparatus. And a pattern detected position is compared witha detection estimating area to extract oversights and wrong detection,thereby it is determined whether or not pattern counting is done asspecified. Consequently, the accuracy for identifying an ending point,that is, a defect position, is improved significantly.

Thus each defect position on a semiconductor device, detected by aninspection apparatus or the like, has come to be identified veryaccurately, quickly, and stably in another apparatus such as an analyzeror the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for describing problems of a conventional cellcounting method;

FIG. 2 is a diagram for describing a unit vector;

FIG. 3 is a basic flowchart of a cell counting method in a firstembodiment;

FIG. 4 is an example of an image displayed on a screen after theflowchart shown in FIG. 3 ends;

FIG. 5 is an explanatory diagram for showing a specimen having acomplicated pattern;

FIG. 6 is an overall configuration of a charged particle beam apparatusin a second embodiment;

FIG. 7 is an overall flowchart of the operation of the charged particlebeam apparatus in the second embodiment;

FIG. 8 is a detailed flowchart of a specimen position adjusting processin the overall flowchart shown in FIG. 7;

FIG. 9 is a detailed flowchart of the pattern counting condition settingstep in the overall flowchart shown in FIG. 7;

FIG. 10 is a detailed flowchart of the step 6 shown in FIG. 7;

FIG. 11 is a detailed flowchart of the step 8 shown in FIG. 7;

FIG. 12 is a diagram for describing a method of visual field movingrange changes with use of an image shifting deflector;

FIG. 13 is an explanatory diagram of describing how an FOV is moved;

FIG. 14 is a detailed flowchart of the step 9 shown in FIG. 7;

FIG. 15 is a detailed flowchart of the step 9 shown in FIG. 11;

FIG. 16 is an example of an SEM image and a CAD image obtained by thecharged particle beam application apparatus in the second embodiment;

FIG. 17 is a configuration of the GUI of the charged particle beamapplication apparatus in the second embodiment;

FIG. 18 is an overall configuration of the charged particle beamapplication apparatus in the second embodiment;

FIG. 19 is a configuration of a major part of each of a focusing ionbeam column and a projection ion beam column;

FIG. 20 is an image displayed on a display screen after cell countingends in a charged particle beam apparatus in a third embodiment;

FIG. 21 is a flowchart of specimen machining in the charged particlebeam application apparatus in the third embodiment;

FIG. 22 is a diagram for describing a relationship between thevariation/foreign matters and errors of a pattern shape;

FIG. 23 is a diagram for describing a relationship between setting anderrors of a unit vector;

FIG. 24 is a diagram for describing a relationship between displacementand errors of a starting point;

FIG. 25 is an overall configuration of a charged particle beamapplication apparatus in a fourth embodiment;

FIG. 26 is a diagram for describing the features of a flowchart of theoperation of the charged particle beam application apparatus in thefourth embodiment;

FIG. 27 is a diagram for describing a relationship between deviationdistribution and error causes;

FIG. 28 is a diagram displayed on an improper unit vector correctingscreen; and

FIG. 29 is a diagram for describing a visual field analyzing method inthis embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

In this first embodiment, a description will be made for the basicconcept of cell counting or bit counting with use of unit vectors withreference the accompanying drawings.

FIG. 3 is a basic flowchart of the cell counting in this firstembodiment. At first, in step 301, an image at a target position of cellcounting is obtained and displayed on a screen. The image may be, forexample, any of an electron beam image such as SEM, TEM, etc., as wellas an optical microscope image, etc. that may be obtained by any method.Typically, an image to be obtained here is a semiconductor specimen asshown in FIGS. 2A and 2B.

In next step 302, necessary cell counting information is set/inputted.The “counting information” mentioned here means information including astarting point of a position (0,0), an address of an ending point, unitvectors, and a reference pattern, which are all needed for cellcounting. In this first embodiment, the apparatus user is premised toinput all those information items. After the processing in step 302, adisplay screen, for example, as shown in FIG. 2A appears. On the screenis displayed the unit vectors a and b, the starting point, the endingpoint, and the graphic information 200 of the reference pattern forpattern matching. The straight lines displayed on the unit vectors a andbare additional ones; they may be omitted in principle. However, if theyexit, the visibility is improved for selecting unit vectors optimal to adisplayed cell pattern.

In the next step 303, a detection estimating area is set. A detectionestimating area means an area in which a pattern to be detected isexpected to exist. Using such a unit vector, a detection estimating areacan be set as an area of which center is assumed to be a point separatedfrom the starting point by an integer multiple of the unit vector. Anaddress corresponding to an integer multiple of the unit vector is givento each detection estimating area. The size of each detection estimatingarea is necessarily to be set greater than precision of the patternmatching, and less than the size of the unit vector. If pattern matchingis carried out only in such a detection estimating area, the patternmatching time is reduced. If pattern matching is done only in adetection estimating area, for example, only in a detection estimatingarea overlapping with the additional lines shown in FIG. 2, the patternmatching time can be much more reduced. A detection estimating area isset with use of, for example, a method for specifying each edge point ofthe detection estimating area displayed on the screen with a mouse. Itis also possible to input the coordinate information of each edge point,but it would be more easier to set/input the information on the GUI. Theuser is not always requested to input the limit of such a detectionestimating area; the apparatus is enabled to set the area automaticallyaccording to a predetermined value.

FIG. 4 shows an SEM image displayed on a screen after the processing instep 303 shown in FIG. 3 is executed. Each white or hatched circledenotes a cell. Reference numeral 401 denotes the starting point forcell counting. The a and b denote set unit vectors. The square 402 meansa reference pattern for pattern matching. This time, a hatched detectionestimating area is selected from among those generated from a startingpoint and unit vectors respectively. In other words, the detectionestimating area consists of cells in an area enclosed by the additionallines 405 and 406, as well as by the additional lines 405′ and 406′passing the ending point (4, 3), and their adjacent cells.

In step 304 shown in FIG. 2, pattern matching is executed according tothe set information. In the detection estimating area, a position wherethe highest consistency degree is recognized is searched according tothe reference pattern and it is identified as a target detected patternposition.

In step 305 shown in FIG. 2, cell counting is executed. Correctlydetected cells are extracted as a result of comparison between thedetected pattern position and the detection estimating area. Then, theextracted cells are counted and the ending point cell is identified.

Next, a description will be made for an embodiment in which cellcounting is done for a more complicated pattern. Depending on thespecimen, a pattern for which cell counting is to be made may becluster-structured or nest-structured; it may not be simple as shown inFIG. 4.

FIG. 5A shows an explanatory view of a cluster-structured pattern. Acluster mentioned here means a pattern in which a plurality of cells arecollected to form a specific pattern and such specific patterns aredisposed cyclically and repetitively. In such a cluster-structuredpattern, two unit vectors are specified, that is, one unit vector a forrepresenting a cluster cycle and the other unit vector (b, c) forrepresenting the patterns in a cluster. In this case, the coordinates ofeach pattern shown in FIG. 5A can be represented by (a, b, c). Forexample, in a cluster that includes a starting point (1), an adjacentcell in the direction of the unit vector b is represented as (0,1,0) andan adjacent cell in the direction of the unit vector c is represented as(0,0,1) with respect to the starting point (1)(0,0,0) respectively.

When executing cell counting during pattern matching, at first thecounting advances in the direction of the additional line 502 (that is,vector a). When the predetermined number of cells are counted, thecluster unit cell counting is ended. Information that how many cells arecounted in the direction of the unit vector a is calculated from boththe information of the ending point on the CAD data and the size of theset unit vector a. Then, a proper starting point in the reached cluster(e.g., the starting point (2) shown in FIG. 5A) and the detectionestimating area 505 are set. Then, cell counting is executed in acluster starting at the starting point set as a base point. Cellcounting in the cluster is executed along the additional lines 503 and504 and the ending point (2, 3, 1) is detected finally. The cellcounting route from the starting point (1) (0,0,0) to the ending point(2, 3, 1) is shown with an arrow 506. In the above description, only oneunit vector is used to specify the cycle of clusters. It is alsopossible to execute cell counting by specifying the reference pattern ofthe cluster itself. In such a case, it is just required to specify acluster reference pattern with a unit vector (a, b) and to specify aposition in the cluster with a unit vector (c,d), etc.

FIG. 5B shows an explanatory view of a nested structure of two types ofpatterns (1) and (2) in which cell counting is to be made. In this case,two types of unit vectors (a,b) and (c,d), as well as a relativeposition vector e between reference patterns are just inputted torepresent nested patterns. When executing cell counting actually in sucha case, at first a proper detection estimating area 501 is set accordingto the specified unit vector (a,b), then cell counting is executed whilemoving the reference pattern in the directions of the horizontal andvertical additional lines from the starting point (1)(0,0) to thedetection estimating area. Here, the additional line with respect to thepattern (1) is shown with a solid line. When the detection estimatingarea 501 is reached, pattern matching with the reference pattern isexecuted to detect the ending point of the pattern (1). If the detectedending point (ending point (2)(2,3)) is proper, a position specified bythe relative unit vector e from the ending point of the pattern (1) isset as the starting point (2) (0,0) of the pattern (2). Then, accordingto the unit vector (c, d) and the ending point (1) on the CAD data, thedetection estimating area 502 is set for the pattern (2). Just like thepattern (1), cell counting is executed at the starting point (2) (0,0)and when the detection estimating area is reached, the ending point isdetected. This completes the description of an example for specifyingunit vectors to enable representing a complicated structure pattern, aswell. As a specimen having such a complicated pattern, for example,there are a microcomputer, a logic system semiconductor device, etc.

Although not illustrated, if image obtaining means, image displayingmeans for displaying the image obtaining means, calculating means forexecuting a flow shown in FIG. 2 for image information obtained by theimage obtaining means, information inputting means for transmittinginformation required for calculation to the calculating means or storagemeans for storing such information, etc. are provided for any ofinspection apparatuses, the apparatus will come to be able to executecell counting as described in this embodiment.

Thus the cell counting method in this embodiment can realize cellcounting with less load of the computer more easily and accurately thanany of the conventional methods.

Second Embodiment

In this second embodiment, a description will be made for aconfiguration of a probe contact type electrical characteristicsevaluation system (Nano-Prober:™)) to which the cell counting methoddescribed in the first embodiment is applied. FIG. 6 shows an overallblock diagram of the nano-prober. The “nano-prober” mentioned here is anelectrical characteristics evaluation system capable of measuring theelectrical characteristics of each finely formed circuit pattern at anano-scale. The nano-prober contacts a minute probe directly to anobject circuit pattern to measure its electrical characteristics.Consequently, when putting a probe in contact with a target point of thespecimen, the probing position is searched by cell counting, thereby thesystem operability is improved. In the following description, a “probe”means a mechanical probe.

At first, a description will be made for an electron optical system usedto observe a specimen 603 to be inspected for defects. The electronoptical system is composed of an illuminating optical system 610 forilluminating and scanning a primary electron beam 601 on the specimen603 and a focusing optical system for detecting secondary chargedparticles generated by electron beam illumination. The illuminatingoptical system 610 is composed of an electron gun 611 for generating aprimary electron beam, condenser lenses 612 and 613 for forming aprimary electron beam respectively, a primary electron beam openingangle limiting iris 614 for limiting an opening angle of the primaryelectron beam, a scanning deflector 615 for scanning the primaryelectron beam on the specimen 603, an image shifting deflector 616 forchanging the position of the primary electron beam on the specimen 603,and an objective lens 617 for focusing the primary electron beam ontothe specimen 603. The secondary electrons 602 generated from thespecimen 603 illuminated by the primary electron beam 601 is detected bythe secondary electron detector 618, etc. And a scanning signal sent tothe scanning deflector 615 is synchronized with a secondary electronbeam detection signal detected by the secondary electron detector 618 toobtain a secondary electron image of the specimen 603.

Next, the driving systems will be described. The specimen 603 is held ona specimen pedestal 624 and the specimen pedestal 624 is held byspecimen pedestal driving means 623. The combination of the specimenpedestal 603 and the specimen pedestal driving means 623 is referred toas a DUT stage. The probe 627 used to measure the electricalcharacteristics of the specimen 603 is held by a probe attachment 626and the probe attachment 626 is held by probe driving means 625. The DUTstage and the probe driving means 625 are formed on the large stage 622respectively. The large stage 622 is provided with driving means in xand y directions (in-plane) and in a z direction (perpendicular),thereby the large stage 622 can drive both the DUT stage and the probedriving means 625 unitarily. The large stage 622 is also disposed on thebase 621. Those driving systems are disposed in a vacuum chamberpartition 620 and drive object devices in a vacuum respectively.

Next, the electrical characteristics measuring system will be described.The specimen 603 is connected to an electrical characteristics measuringinstrument 628 through the specimen pedestal 624 and the probe 627 isconnected to the electrical characteristics measuring instrument 628through an attachment 626 respectively. The probe 627 is put in contactwith the specimen 603 to measure the current-voltage characteristicthereof to calculate a desired characteristic value from the measurementresult. For example, the electrical characteristics measuring instrument628 calculates the resistance value, current value, voltage value, etc.at the contact point of the probe 627. In the case of an analysis of asemiconductor wafer, for example, a semiconductor parameter analyzer isused as an electrical characteristics measuring instrument 628. Themeasurement result of the electrical characteristics measuringinstrument 628 is sent to a control computer 630 and used for stillhigher analysis.

Next, the control system will be described. The control system controlsthe electrical optical systems and driving systems. The control systemis composed of an electron gun control power supply 611′ for supplying adriving voltage to the electron gun 611, a condenser lens 612′ forsupplying a driving voltage to the condenser lens 612, an iris controlunit 614′ for controlling an aperture diameter of the iris 614, adeflector control unit 615′ for supplying a scanning signal to thescanning deflector 615, an image shifting deflector control power supply616′ for supplying a deflection signal to the image shifting deflector616, an objective lens control power supply 617′ for supplying a drivingvoltage to the objective lens 617, a secondary electron detector controlunit 618′ for turning on/off the transmission of the detection signaldetected by the secondary electron detector to the control computer 630,a large stage controlling means 622′ for transmitting a position controlsignal to the large stage 622, a specimen pedestal driving means 623′for transmitting a position control signal to the specimen pedestaldriving means 623, and a probe driving means controlling means 625′ fortransmitting a control signal to the probe driving means 625.

The control computer 630 controls the whole defect analyzing apparatus.Consequently, the control computer 630 is connected to all of theelectron gun control power supply 611′, the condenser lens 612′, theiris 614′, the deflector control unit 615′, the image shifting deflectorcontrol power supply 616′, the objective lens control power supply 617′,the secondary electron detector control unit 618′, the large stagecontrolling means 622′, the specimen pedestal driving means 623′, andthe probe driving means controlling means 625′. The control computer 630also includes storage means 635 for storing software for controllingeach connected component, a user interface 637 for inputting settingparameters of the apparatus, and a display device 636 for displayingvarious operation screens and SEM images. In addition, the controlcomputer 630 also includes a plurality of image processing units 631 to633 and a CAD navigation system 634 for storing wiring layout data(hereunder, to be referred to as CAD image data) of each target specimenand outputting the wiring layout data according to appropriate referenceinformation.

Next, a description will be made for how cell counting is executed inthe apparatus shown in FIG. 6.

At first, the overall flowchart shown in FIG. 7 will be described. Theflowchart shown in FIG. 7 is divided roughly into three sub-flows; analignment flow, a condition setting flow, and an execution flow.

The alignment flow is a flow for adjusting the optical axis of theelectrical optical system. The alignment flow consists of two steps;step 1 for inserting a specimen in the analyzing apparatus and adjustingthe position of the specimen in a mirror body with use of the specimenstage while observing the SEM image and step 2 for correcting the axisdeviation, astigmatic point, and focal point of the electrical opticalsystem while observing the SEM image. After the alignment process, thecondition setting flow begins.

The condition setting flow is a flow for setting conditions required forsubject cell counting. In step 3, the DUT state or large stage 622 isdriven to move the subject specimen so that a desired area including astarting point of cell counting is included in the visual field of theSEM image. In step 4, the following items are set; photographingconditions for an array structure image used for pattern counting, areference pattern image, a positional information of a starting point(0,0), unit vectors, and an address of an ending point (step 4). Thepositional information of the starting point and the address of thestarting point may be set on the wiring layout supplied from the CADnavigation system or may be set on the SEM image actually obtainedthrough the user interface 637. After that, data required foridentifying the starting point of pattern counting is recorded (step 5).Then, photographing conditions for an array structure image used formeasuring stage position setting errors, as well as an analyzablepositional deviation are set (step 6). Then, an address of the endingpoint and the procedure of analyzing or machining to be performed aroundthe ending point are set (step 7).

The condition setting flow is exited when the processings in steps 3through 7 are completed. After inputting the necessary number ofconditions, control goes to the execution flow. At first, the conditionsinputted in step 5 are called to identify a starting point of patterncounting (step 8). Then, the conditions inputted in step 4 are called toexecute pattern counting (step 9). The visual field is moved with use ofthe image shifting deflector until the ending point is reached tophotograph array structure images sequentially (step 10). The patterncounting is still continued. If the moving range of the image shiftingdeflector is exceeded, the specimen stage is moved to cancel the controlvalue change of the image shifting deflector (step 11), then the visualfield movement is continued by image shifting. When the ending point isreached, the conditions inputted in step 7 are called to perform thespecified analyzing or machining (step 12). The execution flow is exitedwhen the processings in steps 8 through 12 are completed. When all theinputted conditions are executed, the flow processings are ended.

Next, the details of each step described above will be described. Atfirst, the specimen position adjusting process in step 1 will bedescribed with reference to FIG. 8. A specimen 603 is put first on thespecimen pedestal 624, then the specimen 603 is inserted into thespecimen chamber with use of the large stage 622. The specimen 603 isthen checked with a low magnification SEM image to adjust the positionof the large stage 622 with respect to the optical axis of the electronbeam illumination system 610. When adjusting the position of the largestage 622, the control values of the probe driving means 625, thespecimen pedestal moving means, the image shifting deflector, etc.should be reset beforehand. After that, the position of each probe isadjusted with respect to the optical axis of the electron beamillumination system 610. Then, the probe driving means 625 is adjustedso that all the probes to be used enter the SEM visual field, then thecontrol values of the probe driving means 625 are recorded. After that,the position of the specimen 603 is adjusted with use of the DUT stagewith respect to the optical axis of the electron beam illuminationsystem 610. At that time, the DUT stage control system 623′ is linkedwith the CAD navigation system 634. Each of the latestinspection/analyzing apparatuses is provided with a CAD navigationsystem in which a device structured layout data (CAD data) is stored. Ifthe user inputs information of an observation point in the CADnavigation system, the specimen stage is controlled to display a SEMimage including the observation point. To use this system, it isrequired to use a plurality of alignment marks disposed on the specimen603 to correct the position setting error when the specimen 603 is puton the specimen pedestal 624.

In step 2, the electron optical system is adjusted by controlling theDUT stage so that the electron optical system adjusting pattern isincluded in the SEM image while observing the adjusting pattern. Thoseadjustments may also be done automatically with use of control software.The adjustments may be done during the processing in step 1.

In step 3, the specimen is moved with use of the CAD navigation system.At first, the starting point is inputted on the CAD data, then the DUTstage is controlled so that the starting point may be included in theSEM visual field. If the apparatus cannot use any CAD navigation system,the user is requested to adjust the DUT stage and move the DUT stage upto a position in which the starting point is included in the SEM visualfield. In that case, the DUT stage should be moved so as to include thestarting point at the top left of the SEM image visual field to obtainbetter visibility.

Next, a description will be made for the details of step 4 (conditionssetting for pattern counting) shown in FIG. 7 with reference to FIG. 9.At first, an array structure image is photographed. A reference patternmay be created from the photographed array structure image or areference pattern image recorded beforehand may also be called. Afterthat, the unit vector initial value is inputted. The unit vector initialvalue may be specified while observing the subject array structure or avalue calculated from both the CAD data and the photographingmagnification of the array structure may be used as the initial value.The inputted initial value is corrected with use of a calibrationsystem. The details of the calibration system will be described later inthe fourth embodiment. Next, a starting point and the address of thestarting point in the array structure are inputted to find a detectionestimating area. After that, a reference pattern and an array structureimage are inputted to the pattern detection system to detect the patternposition. Then, the detection estimating area is compared with thedetected position to find such pattern detection results as correctdetection, oversights, wrong detection, etc. If there are manyoversights and wrong detection occurrence (over a predeterminedthreshold value), the frequency of the occurrence and its relatedinformation are displayed on a screen. A threshold value for determiningwhether to display such information is stored in the storage means 635and the control computer 630 refers to the information. If the patterndetection results do not satisfy predetermined conditions, the patterncounting conditions are adjusted and they are verified again. If thedetection results satisfy the predetermined conditions, the patterncounting conditions are recorded.

In step 5, data necessary for identifying the starting point of patterncounting is recorded. If an array structure image that includes thestarting point of pattern counting is already photographed in step 4,the array structure image may be used. Finally, the coordinates of thestarting point in the array structure image, the array structure imagephotographing conditions, the DUT stage control value, the imageshifting deflector control value are recorded together with the arraystructure image.

In step 6, image photographing conditions used for measuring the stageposition setting error and the analyzable visual field deviation areset. If there is a recipe, it is referred to, then both imagephotographing conditions and visual field moving distance are inputted.FIG. 10 shows a flowchart for verifying whether or not stage positionsetting error can be measured on the conditions. Then, the arraystructure image before the visual field movement is photographed. Aftermoving the visual field with use of the image shifting deflector, thearray structure image is photographed. Because the image shiftingdeflector is high in position setting accuracy, the visual fielddeviation, before and after the visual field movement, can be found fromthe control value of the image shifting deflector. Then, a pair ofimages for which the visual field deviation is already known is inputtedto the analyzing apparatus and it is verified for whether or not thevisual field deviation can be analyzed. If it is analyzable, both of theimage photographing conditions and the visual field deviation arerecorded. If not analyzable, the conditions are changed and they areverified again.

In step 7, the address of the ending point, as well as the analyzingprocedure to be executed around the ending point are inputted. In thecase of an electrical characteristic evaluation apparatus that uses amechanical probe, the point with which the probe is put in contact isspecified and the electrical characteristics to be measured areinputted. When a probe is put in contact with a specimen, the CAD imageis compared with the SEM image to do probing. FIG. 16A shows an exampleof a CAD image. Reference numerals 1600 and 1601 denote a wafer specimenand a plug respectively. An area enclosed with a dotted line is awiring. In FIG. 16A, the wirings 1602 to 1604 in the horizontaldirection are separated from the wiring 1605 in the vertical direction,which connects between wirings 1602 to 1604 in the horizontal direction.A plurality of plugs are formed on each wiring. Each wiring is embeddedin the specimen and it cannot be observed from the SEM image. The probeis put in contact with the surface-exposed plug 1601 to measure theelectrical characteristics to diagnose wire disconnection, etc. Thewirings to be diagnosed are inputted to the CAD navigation system, thenplugs to be measured are output. After that, a CAD image that includethose plugs is displayed, then a position with which the probe is to beput in contact and the electrical characteristics measuring procedureare inputted on the CAD image. A plug assumed to be the ending point ofcell counting is selected from the position with which the probe is putin contact or its adjacent plug. Here, the plug 1601 shown in FIG. 16Ais selected as the ending point. Then, the ending point of patterncounting is calculated on the CAD data according to the starting pointand the address of the starting point inputted in step 4, as well as theunit vector.

When the processings in steps 3 to 7 are completed, the conditionsetting flow is exited. If there is no need to input other conditions,the condition setting flow is also exited.

Steps in and after step 8 are the execution process. At first, theconditions recorded in step 5 are called to control the specimen stageso as to include a starting point in the SEM image visual field. In step8, a flow for adjusting both image shifting and the specimen stage shownin FIG. 11 is included. The detail of this step 8 will be describedlater.

In steps 9 to 11, cell counting is executed from the starting point tothe ending point while moving the SEM image visual field. FIG. 13 showshow the SEM image visual field is moved from the first FOV(Field ofView=visual field) 1301 to the third FOV1303 through the second FOV1302.A frame including the starting point (0,0) identified in step 8 denotesthe first array structure image and its right side frame denotes thesecond array structure image. When moving each FOV, the FOV is moved sothat the bottom right of the visual field before the FOV movementoverlaps with the top left of the visual field after the FOV movement(that is, the ending point before the FOV movement is positioned at thetop left in the FOV after the movement). In the first array structureimage, the first detection estimating area is set based on thepositional information of the address (0,0) and the unit vector, thenfirst pattern matching is carried out, thus the position of the cell ofthe (7,1) address positioned in an overlapped area is specified. In thesecond array structure image, the second detection estimating area isset based on the positional information of the address (7,1) and theunit vector, then second pattern matching is carried out.Above-mentioned procedure is repeated in next array structure image,then finally the position of the end point is detected. So, in the thirdarray structure image, same procedure is repeated. As for the visualfield moving technique of the charged particle beam applicationapparatus in this embodiment, both visual field means and visual fieldmoving distance measuring means are improved. Concretely, a specimenstage is added to the visual field moving means and an image shiftingdeflector are employed for the apparatus. The specimen stage is wide invisual field moving range, but low in position setting accuracy. On theother hand, the image shifting deflector is narrow in visual fieldmoving range, but high in position setting accuracy. Thosecharacteristics are thus taken into consideration to move the visualfield with use of the image shifting deflector (step 10) and thespecimen stage is used only when the visual field moving range of theimage shifting deflector is changed (step 11).

Next, a description will be made for how to change the visual fieldmoving range of the image shifting deflector (step 11) with reference toFIG. 12. At first, a visual field moving vector (Gx, Gy) needed to reacha visual field including an ending point from the array structure imagephotographed last is calculated. Then, the control value of the imageshifting deflector is changed so as to move the visual field only by(Ix, Iy)=−(Gx, Gy). Then, the visual field is moved by (Sx, Sy) with useof the specimen stage to cancel this visual field movement (Ix, Iy). Asa result, the visual field moving range of the image shifting deflectoris moved only by (Sx, Sy). If (Gx, Gy) is larger than the control valuechanging range of the image shifting deflector, a vector (Gx, Gy) isdivided into a plurality of vectors and the above step is repeated.

In step 9, pattern counting is done in each array structure image. FIG.14 shows a flowchart of the pattern counting. The array structure imagephotographed before the visual field movement is determined as the n−1starray structure image and the array structure image photographed afterthe visual field movement is determined as the n-th array structureimage. At first, in the case of n=1, a detection estimating area in then-th array structure image is set according to the starting point, theaddress of the starting point, and the unit vector inputted in step 4.In the case of n>2, a detection estimating area is set according to thepattern detection result in the n−1st array structure image photographedbefore the visual field movement. The n−1st and n-th array structureimages overlap more than the position setting error caused by the imageshifting deflector. Because the position setting accuracy of the imageshifting deflector is high and the setting error is assumed as to beless than ½ of the unit vector, a detection estimating area can be setin the n-th array structure image on the basis of the pattern detectionresults obtained in the n−1st array structure image. Thus a patternposition in the n-th array structure image is identified in patternmatching with the reference pattern image. Then, the detectionestimating area is compared with the detected position to generate suchpattern detection results as correct detection, oversights, wrongdetection, etc. If the pattern detection results satisfy thepredetermined conditions, the pattern detection results are recorded andcontrol goes to the next step. Then, the following predeterminedconditions are set; the rate of correction detection is over a certainvalue, wrong detection and oversights are not distributed like acluster, etc. Those conditions setting will be described later in thefourth embodiment. If the predetermined conditions are not satisfied,the detection estimating area must be corrected. Thus the starting pointand the unit vector are corrected.

After that, the visual field is moved with use of the image shiftingdeflector until the ending point is included in the photographed arraystructure (step 10). If the ending point is not reached within themoving range of the image shifting deflector, the change of the imageshifting deflector control value is canceled with a specimen stagemovement (step 11), then the visual field is kept moved by the imageshifting deflector. FIG. 15 shows the procedure of step 11. After that,the array structure image photographing conditions for analyzing thestage position setting error and the analyzable visual field deviationare called. Then, the array structure image before stage movement isphotographed. Then, the visual field is moved by a predetermineddistance with use of the image shifting deflector and the arraystructure image to be verified is photographed. Those images are used toverify whether or not the visual field can be analyzed. Thisverification step can be omitted. After the visual field is moved by(lx, ly) with use of the image shifting deflector, then the visual fieldis moved by (Sx, Sy) to cancel the visual field movement (lx, ly) withuse of the specimen stage (see FIG. 12), then the array structure imageafter the specimen stage movement is photographed. After that, a visualfield deviation is found between the array structure images before andafter the specimen stage movement. Then, the specimen stage positionsetting error is found from the visual field deviation to correct thevisual field with use of the image shifting deflector or to correct thestarting point in the array structure image for pattern detection tocorrect the visual field.

Here, a description will be made for adjustments of the image shiftingdeflector and the specimen stage to be executed in step 8. Because thespecimen stage is low in position setting accuracy, the adjustment ofthe image shifting deflector by the specimen stage in step 11 mightresult in fail. So, in order to reduce the number of this adjustments asmany as possible, the flow shown in FIG. 11 is executed in step 8. Atfirst, the specimen stage is moved according to the setting datainputted in step 5. The visual movement vector (Gx, Gy) for reaching theending point from the starting point is obtained according to thesetting data inputted in step 4, then the visual field is moved only by(Ix, Iy) in the direction of −(Gx, Gy) with use of the image shiftingdeflector. Then, the visual field is moved by (Sx, Sy) with use of thespecimen stage to cancel the visual field movement (Ix, Iy) by the imageshifting deflector and the array structure image is photographed on thesame conditions as those in step 5. At this time, there is a visualfield deviation caused by a specimen stage position setting errorbetween the array structure image photographed in step 5 and the arraystructure image photographed in step 8. This visual field deviation isthus analyzed by the visual field deviation analyzing system to identifythe coordinates of the starting point on the photographed arraystructure image.

When the ending point is reached, the inputted electricalcharacteristics analysis process is executed (step 12). Hereunder, thedetails of the analysis process will be described. At first, theposition with respect to the CAD image (FIG. 16A) used in step 7 isadjusted according to the SEM image of the array structure image (FIG.16B) that includes the ending point and its pattern detection results.FIG. 16C shows a display example of an SEM image and a CAD image thatare put one upon another. This display makes it possible to analyze theelectrical characteristics of the specimen while confirming the internalspecimen device structure, thereby the specimen device can be used moreeasily. After that, the tip of a probe is moved into the visual field ofthe SEM image with use of the probe driving means 625. The probe movingdistance up to the visual field of the SEM image is calculated by givingconsideration to both of the visual field movement and the DUT stagevisual field movement by the image shifting deflector. The positionsetting accuracy of the probe driving means is several μm and the visualfield diameter of the SEM image is estimated to be several tens μm, sothat it is possible to move the probe into the visual field of the SEMimage. Confirming that all the probes to be used are included in the SEMimage, the probing process is started. Confirming that each probecontact is done correctly with the electrical characteristics, the setelectrical characteristic measurement is executed. At this time, thesubject array structure image should be photographed on the conditionsfor obtaining visual field deviation analyzing image just after theending point is identified so as to be prepared for a change of the DUTstage in position to be caused by such an external disturbance asdrifting.

The processings in steps 8 through 12 are all required to be completedfor the present. After all the inputted conditions are executed, all theprocesses are ended.

Finally, FIG. 17 shows an example of a control screen. The controlscreen can display an array structure image, a CAD image, and those twoimages that are put one upon another. The control screen can alsodisplay a reference pattern, a unit vector, and a starting point thatare displayed together with an array structure so as to be put in layers(parameter input screen space). Pattern detection results can also bedisplayed together with an array structure image and a CAD image inlayers (pattern detection results display screen space). There is also acontrol screen on which an address assigned to each pattern can beconfirmed (counting result display screen space).

As described above, the probe contact type characteristics evaluationapparatus in this embodiment makes it possible to improve the cellcounting accuracy, thereby the accuracy for probing at a target positionis improved. Furthermore, the probing time is also reduced.

This Embodiment

In this third embodiment, a description will be made for a case in whicha pattern counting system of the present invention is applied to aspecimen machining apparatus that uses an ion beam.

FIG. 18 shows a basic configuration of an ion beam machining apparatus.The ion beam machining apparatus is composed of an ion beam illuminatingoptical system 1810 for illuminating an ion beam 1811 onto such aspecimen 1876 (object to be machined) as a semiconductor wafer,semiconductor chip, or the like, an ion beam illumination optical systemcontrol unit 1812 for controlling the operation of the ion beamilluminating optical system 1810, a specimen stage 1870 for mounting aspecimen 1876 and moving an observation area of the specimen 1876 intoan ion beam illuminating area, a specimen stage control unit 1871 forcontrolling the position of the specimen stage 1870, a manipulatorcontrol unit 1832 for controlling a manipulator 1830, a deposition gassupply source 1860 for supplying a sedimentary gas (deposition gas)around the observation area of the specimen 1876, a deposition gassupply control unit 1861 for controlling the deposition gas supplysource 1860, an electron beam illuminating optical system 1820 forilluminating a primary electron beam 1821 for SEM images onto thesurface of the specimen 1876, an objective lens 1822, an electron gun1823, a secondary electron detector 1825 for detecting secondaryelectrons discharged from the surface of the specimen 1876, an SEMilluminating optical system control unit 1824 for controlling theelectron beam illuminating optical system, a control computer 1840 forcontrolling the whole ion beam machining apparatus, an A/D converter forconverting output signals from the secondary electron detector 1825 toA/D signals, an image operation unit 1850 for processing output signalsof the secondary electron detector 1825 converted to digital datathrough A/D conversion, etc.

In the ion beam machining apparatus, the incoming directions of theprimary electron beam 1821 and the ion beam 1811 with respect to thespecimen 1876 are determined by the direction in which the cross sectionof the specimen is to be exposed and to be formed into a thin film. Thisis why the specimen stage 1870 is provided with a stage tiling functionwith respect to the ion beam illuminating optical axis and a rotatingfunction (θ stage) with respect to the stage center axis. Thus bothdeclining angle and rotating angle of the position of the specimen 1876in the three-dimensional directions, as well as the surface of thespecimen 1876 can be controlled freely with respect to the ion beamaxis. Consequently, it is possible to set freely the ion beamillumination position (processing position) on the surface of thespecimen 1876, as well as the illuminating angle and rotating angle ofthe ion beam with respect to the surface of the specimen 1876. The ionbeam illuminating optical system 1810, the specimen stage 1870, thedeposition gas supply source 1860, the ion beam illuminating opticalsystem 1810, and the secondary electron detector 1825 are disposed in avacuum chamber 1800 to be highly evacuated.

The control computer 1840 controls the whole ion beam machiningapparatus including such charged particle optical systems as the ionbeam illuminating optical system 1810, the electron beam illuminatingoptical system 1820, etc. or the mechanical systems of the whole ionbeam machining apparatus such as the specimen stage 1870, themanipulator 1830, etc. generally. Thus the control computer 1840includes storage means 1855 for storing software for controlling each ofthe connected components, a user interface 1842 used for the user toinput apparatus setting parameters, and a display 1841 for displayingvarious types of operation screens and SEM images. In addition, theimage operation unit 1850 includes a plurality of image processing units1851 to 1853 and a CAD navigation system 1854 for handling wiring layoutdata (hereunder, to be referred to as CAD image data) of the objectspecimen.

The ion beam illuminating optical system 1810 shown in FIG. 18 uses afocused ion beam (FIB). However, a shape forming (projection) ion beam(PJIB) may be formed with the same mirror body. FIG. 19A shows aconfiguration of the major part of the focused ion beam (FIB)illuminating optical system that uses a focused ion beam for machiningspecimens. An ion beam output from the ion source 1813 is passed througha beam limiting aperture 1814, a focusing lens 1815 for suppressing andfocusing the spread of the ion beam, and an objective lens 1817 forfocusing the ion beam on the specimen 1876 so as to form a focused ionbeam 1811. This ion beam 1811 scans on the specimen 1876 through thedeflector 1816 to machine the specimen 1876 in accordance with thescanning shape. The focused ion beam may also be used as observingmeans. The focused ion beam scans the surface of the specimen 1876 andthe secondary electron detector 1825 detects secondary electronsgenerated from the surface of the specimen 1876. Then, the secondaryelectrons are synchronized with the scanning signal to form and displayimages.

FIG. 19B shows a configuration of a major part of the shape forming(projection) ion beam (PJIB) illuminating optical system. The ion beamemitted from the ion source 141 is illuminated onto a projection maskingplate 1819 through a beam limiting aperture 1814 and an illuminatinglens 1815 respectively, then the ion beam passing through a patternaperture 1818 of the masking plate 1819 is projected onto the surface ofthe specimen 1876 put on the specimen stage 1870 through a projectionlens 1817. The surface of the specimen 1876 is machined almost similarlyto the pattern aperture 1818 due to the ion beam formed as describedabove.

Next, the procedures of specimen machining realized by the ion beammachining apparatus in this embodiment will be described with referenceto FIGS. 7, 20, and 21.

Basically, the specimen machining procedures of the ion beam machiningapparatus in this embodiment are almost the same as those of the chargedparticle beam application apparatus in the second embodiment. In thefollowing description, therefore, only the machining process specific tothe ion beam apparatus will be described step by step. Because thisapparatus can obtain both SEM and SIM images, any of the SEM and SIMimages can be used as an array structure image used for cell counting.Concretely, a request to select either a SEM or SIM image is displayedon the display device 1841 and the control computer 1840 switchesbetween the ion beam illuminating system and the electron beamilluminating system according to the response of selection inputtedthrough the user interface. The advantage for using the SEM image isless damage on the surface of the specimen. In the case of the SIM imageobservation using an ion beam as an incoming beam, the surface of thespecimen is trimmed gradually during observation. To protect the surfaceof the specimen from damages, the SEM image should be selected. Thedisadvantage for using a SEM image as an array structure image in theion beam machining apparatus in this embodiment is a deviation to occurin a machining position (that is, ion beam illuminating position) if theSEM/SIM image visual field is deviated. To avoid such a trouble,therefore, the visual field of the SEM/SIM image should be adjusted atthe required accuracy before the specimen machining begins. To adjustthe visual field at such an accuracy, for example, it is needed toobtain proper alignment mark SIM and SEM images, the alignment markcoordinates on each of the obtained SEM and SIM images are compared withthe alignment mark absolute coordinates to calculate the subject visualfield deviation. If an estimated visual field deviation is larger thanthe accuracy of required machining position setting, the SIM imageshould be selected.

After selecting an image used as an array structure image, the specimenposition is adjusted while observing the image. Then, to link thespecimen stage control unit 1871 with the CAD navigation system 1854,the position setting error that might occur when a specimen 1876 is puton the specimen stage 1870 is corrected with use of a plurality ofalignment marks disposed on the specimen 1876.

In parallel to the adjustment of the above described first chargedparticle optical system or after the adjustment, the second chargedparticle optical system is adjusted. In case where a SIM image is usedas an array structure image, it is only needed to adjust the ion beamilluminating optical system 1810 as the charged particle optical system.At that time, the following two conditions should preferably be setbeforehand; one of the conditions is a specimen observing FIBilluminating condition for reducing the current flow by narrowing thebeam diameter and the other condition is a specimen machining FIBilluminating condition for increasing the current flow by widening thebeam diameter. In case where a SEM image is used as an array structureimage or in case where both SEM and SIM images are to be used, both theion beam illuminating optical system 1810 and the electron beamilluminating optical system 1820 are adjusted. In this case, afteradjusting each of the illuminating systems, the visual field deviationsof the ion beam illuminating optical system 1810 and the electron beamilluminating optical system 1820 are calculated and corrected. Tocorrect those visual fields, for example, the image shifting deflectoris driven so that the deflection in the deflector becomes equal to eachof the visual field deviations. In case where a PJIB is used to machinea specimen while observing the specimen with a SEM image, eachilluminating system is adjusted, then the visual field deviation betweenthe illuminating systems is corrected. Then, the specimen is machinedwith an ion beam and the machining shape is observed with a SEM image tomeasure the visual field deviation between the illuminating systems,thereby the deviation is corrected with use of the image shiftingdeflector.

The processes in steps 3 to 6 are almost the same as those described inthe first embodiment except for that the image type used for observingthe specimen structure and the specimen stage type used for moving thespecimen are different, so that the description for the processes willbe omitted here.

In step 7, specimen machining procedures executed around an ending pointare inputted. Then, a device structure of which cross sectional image isto be observed is inputted to the CAD navigation system and the surfacestructure existing on the device structure is output. After that, theCAD image including the surface structure is displayed and bothmachining procedure and machining position are specified on the CADimage. The ending point for pattern counting is also inputted on the CADimage here. Then, the address of the ending point is calculatedaccording to the starting point, its address, and the unit vectorinputted on the CAD data respectively.

Next, a specific flow of pattern counting in step 8 will be described.In the specimen machining, both incoming and scanning directions of bothprimary electron bean 601 and ion beam 1811 are determined by thedirection in which the cross section of the specimen to be exposed andto be thin-filmed. The rotating mechanism of the XY in-plane is adjustedwith respect to the specimen stage 1870 in accordance with thoseconditions. If a specimen is rotated after pattern counting, the endingpoint might be lost. To avoid this trouble, the specimen rotating angleshould be set before pattern counting. Thus the specimen machiningconditions are called to find an in-plane rotating angle, then thespecimen is rotated with use of the specimen stage control unit 1871.

After that, the specimen stage 1870 is controlled so as to include thestarting point in the visual field. And because the specimen stagecontrol unit 1871 is linked with the CAD navigation system 1854, thespecimen stage control value in the XY direction, inputted before thespecimen rotation (step 5) is converted automatically to that to be usedafter the specimen rotation (step 8). Furthermore, the visual field ismoved with use of the image shifting deflector as described in the firstembodiment and the specimen stage is controlled to cancel the visualfield movement, then the array structure image including the startingpoint is photographed. If there is a rotating angle difference betweenthe array structure image photographed in step 5 and the array structureimage photographed in step 8, the array structure images are rotated toeliminate the angle difference between the images, then to correct thevisual field deviation between the images. If a specimen stage rotatingangle setting error is expected at this time, it may be corrected withan image processing method that can analyze the parallel movingdistance, angle difference, and reduced scale between images. Then, thecoordinates of the starting point in the array structure imagephotographed in step 8 is identified from both the visual fielddeviation between images and the coordinates of the starting point inthe array structure image recorded in step 5.

In step 9, pattern counting is executed in each array structure image.At first, the reference pattern and the unit vector are correctedaccording to the specimen rotating angle set in step 8. Then, adetection estimating area is generated according to the corrected unitvector, as well as the starting point and the address of the startingpoint identified in step 9. Then, the subject pattern position in thearray structure image is detected with use of the corrected referencepattern. All the processes other than the above ones are almost the sameas those in step 9 described in the first embodiment.

The processes in steps 10 and 11 are executed in almost the sameprocedures as those in the first embodiment; the image type used forspecimen structure observation and the specimen stage controlling meansin this embodiment are only the different items from the firstembodiment.

In step 12, the machining process inputted in step 7 is executed.According to the array structure image including an ending point and itspattern detection result, the position with respect to the CAD imageused in step 7 is adjusted. FIG. 20 shows an example of an imagedisplayed on the display means 1841 just before the machining in step 12begins when the ending point is reached as a result of precedingcounting. In FIG. 20, the screen displays a CAD image around an endingpoint, as well as a SEM image that is put on the CAD image. Referencenumerals displayed on the screen are defined as follows; 2000 denotes aspecimen, which is, for example, a divided part of a semiconductor chip,a semiconductor wafer, or the like and 2001 denotes a wiring plug, 2002to 2005 denote wirings. 2006 denotes a plug to be machined. 2007 denotesa marking formed with an illuminated electron or ion beam to identify aplug to be machined.

FIG. 21 shows an example of ion beam machining executed in step 12. Instep (a) shown in FIG. 21, a machining ion beam 2101 is illuminated ontoboth sides of the marking 2103 to form a hole 2101. 2104 denotes a plugto be machined and it is equivalent to 2007 shown in FIG. 20. Hereunder,a groove for connecting two holes to each other is formed in step (b),then a cuneiform specimen piece 2106 is formed with an illuminated ionbeam while the stage is tiled in step (c). In step (d), the manipulator1830 is driven to put the tip of a probe 2107 in contact with thecuneiform specimen piece 2106 to form a deposition film for connectingthe tip of the probe to the cuneiform specimen piece with an illuminatedion beam 2102. In step (e), a connecting part is cut off with anilluminated ion beam from a parent material for removing the cuneiformspecimen piece 2106 and the specimen piece respectively. In step (f),the specimen piece is lifted out from the parent material by operatingthe manipulator 1830. The specimen piece 2106 stuck to a probe is movedto a sample carrier 2109 in step (g) and put in a fixing groove 2110 onthe surface of the sample carrier in step (h). Then, in steps (h) and(g), the deposition film 2108 for sticking the probe 2107 and thespecimen piece 2106 to each other is removed with an illuminated ionbeam 2101, thereby the probe 2107 is separated from the specimen piece2106. In step (j), a side of the plug 2104 is trimmed with anilluminated ion beam 2101 to form a thin film specimen having a crosssectional face of a plug finally.

The processes in steps 8 to 12 are all that are required for thepresent. When all the inputted conditions are executed, all theprocesses are ended.

As described above, the ion beam machining apparatus in this embodimentcan improve the accuracy of cell counting, thereby the accuracy ofsampling for target structures is improved. Furthermore, the samplingtime is also reduced.

Fourth Embodiment

In this embodiment, a description will be made for a configuration of acharged particle beam apparatus provided with a function for correctingcell counting errors. When correcting such a cell counting error, adetection estimating area is used. The counting conditions resettingfunction to be described later in this embodiment may be applied for theapparatus in any of the second and third embodiments. In thisembodiment, however, the explanation will be focused on a measuringapparatus (such as a measuring system, defect review system, or externalview inspection system) using a scanning electron microscopeparticularly on the premise of the resetting function is installed.

At first, error causes to be picked up in this embodiment will bedescribed with reference to FIGS. 22 through 24. FIG. 22 shows a case inwhich a cell counting error occurs, since patterns are not shapeduniformly and there are many foreign matters included in the obtainedarray structure image. In FIG. 22, it is premised that a distorted bit2202, as well as many foreign matters 2003 are included in the subjectarray structure image in addition to a normal bit 2201. The foreignmatters to be included in specimens are as follows, for example; aforeign matter 2203 detected at a position in which no bit is formed anda foreign matter 2204 detected at a bit formed position. In the case ofan array structure image that includes such a pattern distortion andmany foreign matters, oversights and wrong detection occur even inpattern matching performed based on a reference pattern 2205. Anoversight mentioned here means that no pattern is detected in an area2206 even when a detection estimating area (represented by a dotted linerhombus in FIG. 22) is set. Wrong detection means that a pattern isdetected in an area (e.g., area 2207) other than the target detectionestimating area. In case 2208 where a pattern is detected actually inthe target detection estimating area in pattern matching, the detectionis referred to as correct detection. A rate of oversights and wrongdetection is considerably low, pattern counting can be continued onlywith correctly detected patterns. If the rate of oversights and wringdetection is high, however, it is required to review the array structureimage photographing conditions (magnification, fetching time, etc.),reference pattern setting conditions (shape, size, etc.), imageprocessing conditions (threshold value, etc.) for pattern matching.

FIG. 23 shows an explanatory diagram for a case in which oversights andwrong detection occur due to the first setting of an improper unitvector. In FIG. 23, additional lines 2304 and 2301 are extended lines ofunit vectors a and b, and dotted lines 2205 and 2202 denote propercoordinate axes of the array structure image shown in FIG. 23. Becauseof such improper unit vectors, a detection estimating area 2307determined by the unit vectors is separated from an original detectionestimating area 2308. And this separation comes to cause oversights andwrong detection. As shown in FIG. 23, a deviation caused by improperunit vectors increases in proportion to the extension of the distancefrom the starting point (0,0). In this case, the unit vectors must becorrected.

FIG. 24 shows a concept diagram for showing oversight and wrongdetection occurrence caused by displacement of an starting point. Forexample, when the starting point of the n−1th photographed arraystructure image is taken over to the n-th photographed array structureimage, the starting point is transmitted wrongly sometimes due to avisual field moving error. In FIG. 24, if the center coordinates 2405 ofan actual starting point are displaced from the correct centercoordinates 2404 when cell counting is started at the starting point(x1,y1) 2401, then the detection estimating area 2403 (displayed with asolid line) is formed away from the correct detection estimating area2402 (displayed with a dotted line) and the subsequent cell counting ismade while the displaced starting point 2406 is left as is. This is whya correcting function is needed to correct such a displacement of astarting point.

FIG. 25 shows an explanatory diagram of an overall configuration of anelectron beam application apparatus in this embodiment. The scanningelectron microscope in this embodiment is roughly composed of a scanningelectron microscope 2500, a control unit 2510 for controlling themicroscope 2500, a computer 2520 for controlling the host of the controlunit 2510, and a user interface 2530 for inputting necessary informationand setting conditions for the operation of the computer.

The scanning electron microscope 2500 is composed of an electron source2510 for generating a primary electron beam, a condenser lens 2502 forcontrolling a cross-over position of the generated primary electronbeam, a limiting iris member combined with controlling of the cross-overposition of the condenser lens 2502 to adjust a current flow of theprimary electron beam, a scanning deflector 1504, an objective lens2505, a specimen stage 2507 for holding a specimen 2506 to be measured,a detector 2508 for detecting secondary electrons or back scatteredelectrons generated from the primary electron beam, etc. The controlunit 2510 is actually composed of a plurality of microcomputers forcontrolling driving power supplies and power supplies of the componentsof the scanning electron microscope 2500. The control unit 2510 suppliesnecessary current, voltage, or control signals to the scanning electronmicroscope 2500 to actually operate the scanning electron microscope2500. The computer 2520 computes control information required to operateindividual components of the SEM systematically (e.g., cooperativecontrol information of the components of the scanning electronmicroscope 2500 required to operate the whole apparatus on theconditions set and inputted from the user interface 2530) and transmitsthe information to the control unit 2510. The computer 2520 alsosynchronizes the detection signal of the detector 2508 with themodulation frequency of scanning signals to compute the two-dimensionalintensity distribution data of the secondary electrons or back scatteredelectrons and display the result on a display device (not shown). Thecomputer 2520 incorporates an operation device and a memory used toexecute various types of computing described above respectively. Inaddition, the computer 2520 incorporates an external storage 2521 forstoring obtained two-dimensional distribution data and various types ofsoftware executed by the operation device. Signal lines 2522 and 2523are used to connect the external storage device 2521 to the computer2520.

Next, a description will be made for the operation of the chargedparticle beam application apparatus in this embodiment with reference toFIGS. 7 and 26. The charged particle beam application apparatus in thisembodiment operates basically in the same flow as that shown in FIG. 7;Only a difference from the flow shown in FIG. 7 is the operation shownin FIG. 26 added to step 9. Consequently, other operations in othersteps are the same as those described in the second embodiment, so thatthe description will be omitted here.

FIG. 26 shows an execution flow in determination steps for whether ornot the rate of correctly detected patterns is within δ when patterncounting in an array structure image is ended. The threshold value δ isvaried among patterns subjected to cell counting, so that the externalstorage 2521 stores both δ values and ID numbers of specimens (i.e. thelot number) so that they can be referred to mutually.

In case where the rate of correctly detected patterns is less than thethreshold value, the computer 2520 estimates the cause of the error.This estimation is made in a step of obtaining the distributioninformation of a deviation between a detection estimating area and apattern detected position and a step of estimating the error cause. Thedeviation distribution information is obtained by referring to thetwo-dimensional distribution data stored in the external storage 2521 toread the oversight/wrong detection occurred position coordinateinformation, as well as both starting and ending points in the subjectFOV. Just like the second embodiment, if many oversights and wrongdetection occur particularly, the frequency of oversights and wrongdetection, as well as similar information are displayed on a screen. Athreshold value for determining whether to display those informationitems on a screen is stored in the memory and external storage 2521provided in the computer 2520 respectively. If the threshold value isexceeded, the image data of the cell counted area is displayed on thedisplay device. Because a pattern of an area in which many oversightsand wrong detection occur can be checked on a real image, the usabilityof the operation of the apparatus is improved.

Next, principles for identifying an error occurrence cause fromdeviation distribution information will be described with reference toFIG. 27. In FIGS. 22 through 24, the following error causes are shown.

(1) There are many distortions and foreign matters detected in anobtained array structure image. (2) Improper setting of unit vectors (3)A starting point of cell counting is displaced.

In any of the above cases, it is estimated that the number of oversightsand wrong detection are distributed as shown in FIG. 27 with respect toa distance from a starting point of cell counting (a distance from thestarting point of positional coordinates of executed pattern matching,represented by the number of pixels).

For example, if there are many distortions and foreign matters detectedin obtained two-dimensional distribution data, the distribution becomescompletely at random with respect to the distance from the startingpoint, since the number of oversights and wrong detection do not dependon the occurrence position. If a unit vector is improper, the distortionincreases in proportion linearly to the distance from the startingpoint. In addition, if displacement depends on starting points of cellcounting, the frequency of occurrence is almost fixed with respect tothe distance from the subject starting point, since cell countingadvances while the displacement from the center of the reference patternis left as is. Consequently, each error cause can be identified bycalculating how much the frequency of oversight and wrong detectionoccurrence depends on the distance from the subject starting point andby determining the error type. Such an identification step is executedwhen the operating means in the computer 2520 applies actually a properfitting curve to the displacement distribution. When such an error causeis identified, counting conditions are reset and cell counting isrestarted.

Next, the counting conditions resetting procedure for restarting cellcounting will be described.

At first, if the rate of distortions, foreign matters, oversights, andwrong detections is high, the array structure image photographingconditions (magnification, fetching time, etc.), the reference patternsetting conditions (shape, size, etc.), and pattern matching imageprocessing conditions (threshold value, etc.) are reset. In such a case,when the error cause estimating step is ended, control goes back to step4 or 9 shown in FIG. 7 to restart the processing.

If a unit vector is improper, the display screen of the user interface2530 is switched over to the unit vector correcting screen, thereby thedrawings shown in FIGS. 2A and 2B, as well as the unit vector resettingrequest are displayed on the correcting screen. Hereinafter, thecorrecting procedure for the resetting will be described with referenceto FIGS. 28A and 28B. In the Fourier conversion image (FIG. 28B) of thearray structure image (FIG. 28A) are generated various peakscorresponding to the array structure periodicity. Thus a peak isselected from among those peaks. The selected peak is the closest one tothe position of a peak calculated from the initial value of the unitvector. A unit vector calculated from the center of the selected peak isdetermined as a corrected unit vector. The self correlation image of thesubject array structure image may also be used to correct the unitvector. Also in this case, among the peaks to appear in the selfcorrelation image, a peak is selected and the selected peak is theclosest one to the position of a peak calculated form the initial valueof the unit vector. Then, a unit vector calculated from the center ofthe selected peak is determined as a corrected unit vector. If the userresets the unit vector in the above procedure, the charged particle beamapplication apparatus restarts cell counting according to the reset unitvector.

If a starting point of cell counting is displaced, the starting point iscorrected in the following procedure. At first, an average displacementbetween the center of the detection estimating area and the detectedposition is calculated in the position of the correct detection and theresult is assumed as a displacement value of the starting point. Then,according to the calculated displacement, the starting point in the n-tharray structure image is corrected.

If a lower magnification and a shorter fetching time are set for thearray structure image photographing conditions, the pattern countingtime can be reduced. In that case, however, the detection result becomesunstable due to the image SN lowering. If a plurality of patterns isincluded in the reference pattern, the variation of the patterns isaveraged, thereby the detection result is stabilized. In that case,however, the analyzing time increases. The shape of the referencepattern can be selected from any of squares, rectangles, circles, etc.,so that it should be optimized appropriately to the subject specimen. Ifthe reference pattern is machined properly, the detection results may bestabilized in some cases. For example, a plurality of patterns areremoved from the subject array structure image and those patterns areadded up and averaged to obtain a reference pattern. Then, the referencepattern is masked properly to extract only an area to be subjected topattern matching. As for image processings, in the case of the mutualcorrelation method and the least square method, a threshold valuematching with the reference pattern should be optimized in accordancewith the subject image. And those conditions are optimized to improvethe rate of correct detection of patterns.

While a description has been made for an operation flow of the chargedparticle beam application apparatus in this embodiment, the error causeestimating step and the counting conditions resetting step shown in FIG.26 may be executed during or after cell counting. If softwarecorresponding to both of those operation modes is built in the computer2520 or external storage device 2521 beforehand so that the user canselect either of the modes (e.g., a request for selecting either of theoperation modes is displayed on the user interface 2530 before startingthe flow shown in FIG. 26), the operability of the charged particle beamapplication apparatus will be improved.

As for image processings, in addition to pattern matching, imageprocessings are needed to measure the moving distance of the whole arraystructure image. If there is no error in the specimen stage positionsetting, the same visual field is photographed both before and after thespecimen stage movement. However, because there is an error in thespecimen stage position setting usually, a visual field deviation comesto occur. If this visual field deviation is assumed to be larger thanthe subject unit vector, it cannot be measured in pattern matching. Thisis why the present invention has employed a visual field analyzingmethod that uses phase difference calculation. This method ischaracterized in that only the same patterns are detected withoutdetecting similar patterns. Thus it is possible to analyze a visualfield deviation even between array structure images having a largervisual field deviation respectively than the subject unit vector.

Here, the visual field deviation analyzing method employed this timewill be described with reference to FIG. 29. Assume now that there aretwo discrete images S1 (n, m) and S2 (n, m) with a visual fielddeviation D=(Dx, Dy) therebetween. At this time, S1 (n, m)=S2 (n+Dx,m+Dy) is satisfied. The result of the two-dimensional discrete Fourierconversion of the S1 (n, m) and S2 (n, m) is described as S1′ (k, i) andS2′ (k, i). Because there is a formula F{S(n+Dx), m+Dy}}}}=F{S(n,m)}exp(iDx.k+iDy.l) for the Fourier conversion, the converted result canbe varied to S1′ (k, l)=S2′ (k, l)exp(iDx.k+iDy.l). In other words, thevisual field deviation between S1′ (k, l) and S2′ (k, l) is representedby a phase difference exp (iDx.k+iDy.l)=P′ (k, l). Because P′ (k, l) isalso a wave of which cycle is (Dx, Dy), a peak like δ appears at theposition of (Dx,Dy) in an analyzed image P(n,m) obtained by applyinginverse Fourier conversion to the phase difference image P′ (k, l). Atthis time, the amplitude information is not removed completely; a log or√ processing is applied to the amplitude content of the S1′ (k, l).S2(k, l)*=|S1′| |S2′|exp (iDx.k+iDy.l) to calculate an image in which theamplitude content is suppressed. And even when inverse Fourierconversion is applied to the image, a peak like δ appears at theposition (Dx, Dy) of the visual field deviated vector, so that visualfield deviation analysis may be done for the image. Because a peak likeδ appears at (−Dx, −Dy) even when Fourier conversion is applied to thephase difference image P′ (k, l), visual field deviation analysis may bedone for an image obtained by applying Fourier conversion to the phasedifference image P′ (k, l). And because it is assumed that only a peaklike δ exists in the analyzed image P (n, m), the position of the peaklike δ can be obtained accurately down to the decimal point throughcalculation of a center of gravity or function fitting. And because allthe contents other than the δ-like peak can be regarded as noise, it ispossible to assume the rate of the δ-like peak intensity to theintensity of the whole analyzed image P (n. m) as a consistency degree.The upper/lower limit value used for determination of such a consistencydegree is stored in the external storage device 2521 or computer 2520.

In the case of the conventional visual field deviation analyzing method,it is difficult to evaluate the reliability of visual field deviationanalysis results and frequency contents required for analysis areinsufficient. As a result, even wrong visual field deviation output isused for an analysis/calibration flow as is. However, employment of thevisual field deviation analyzing method described above enables thelower limit of consistency degree to be set and images to bephotographed again automatically if the consistency degree is under thelower limit.

The photographing conditions should be varied between the arraystructure image to be analyzed for visual field deviation and the arraystructure image used for counting the number of patterns. The arraystructure image used for counting the number of patterns shouldpreferably be photographed at a low magnification to reduce the countingtime while the array structure image to be analyzed for visual fielddeviation should preferably be photographed at a rather highmagnification so as to enable differences among individual patterns tobe observed. Whether or not analysis is possible depends on the visualfield deviation between images. The more the visual field deviationincreases, the more the visual field common among images decreases,thereby the analysis becomes difficult. If the analyzable visual fielddeviation becomes smaller than the stage position setting accuracy, aplurality of array structure images of which visual fields are shiftedwith use of the image shifting deflector are photographed after thespecimen stage is moved. Then, the specimen stage position setting erroris analyzed.

The photographing conditions of an array structure image used foranalyzing its visual field deviation are optimized as follows. At first,a visual field analysis is executed between the array structure image1202 photographed before specimen stage movement and the array structureimage 1203 photographed by shifting its visual field with use of theimage shifting deflector. At that time, the visual field deviationshould be within the error of the specimen stage position setting or so.If the subject visual field deviation cannot be analyzed, thephotographing conditions and the visual field deviation are changed andthey are verified again.

After the photographing conditions for the array structure image usedfor analyzing the visual field deviation are determined, the arraystructure image 1202 (FIG. 12A) before the specimen stage movement isphotographed. Then, the control value of the image shifting deflector ischanged and the specimen stage is moved to cancel the visual fieldmovement with the control value. After that, the array structure image1205 (FIG. 12B) after the specimen stage movement is photographed. Then,the visual field deviation from the array structure image 1202 beforethe stage movement is analyzed to find a specimen stage position settingerror, then the error is corrected. This error correction may be done bymoving the visual field with use of the image shifting deflector or bycorrecting the detection estimating area in the array structure imagephotographed after the specimen stage movement.

In addition to the visual field deviation between images, differencesmay be found in rotation and reduced scale due to the distortion aroundan electromagnetic field lens. In such a case, the visual fielddeviation/rotation/reduced scale analyzing method should preferably beemployed, since the method can analyze both rotation and reduced scaletogether with the visual field deviation between images. In addition,the filter/parameter can be adjusted so as to detect only the samepatterns without detecting similar patterns. In this case, however, theadjustment is required for each image and how to make such an adjustmentmust also be know beforehand.

As described above, the charged particle beam application apparatus inthis embodiment can correct cell counting errors to improve the accuracyof cell counting more than any of conventional techniques. And the errorcorrecting function described above can apply to the apparatus describedin any of the second and third embodiments, as well as to generalcharged particle beam apparatuses.

According to the present invention, therefore, it is possible toidentify defect positions in a memory very accurately, quickly, andstably, although it has been difficult conventionally. In addition,because the TAT of the defect position transmission in both inspectionand analyzing apparatuses is improved significantly, the defectanalyzing TAT in process development is improved.

1. A charged particle beam apparatus, including: a function fordetecting secondary charged particles generated from a specimenilluminated by a charged particle beam; and a function for counting thenumber of predetermined patterns appeared between a specific startingpoint and an ending point on said obtained image data, wherein saidapparatus further includes: a charged particle optical system forobtaining said image data; a counting device for counting the number ofsaid appeared predetermined patterns with respect to said image data;information inputting means for setting a unit vector, which is a unitfor specifying a coordinate system to represent said starting point andan address of said ending point; and displaying means for displayingsaid image data, wherein said counting means counts the number of saidappeared predetermined patterns according to said unit vector.
 2. Theapparatus according to claim 1, wherein a moving direction of each ofsaid predetermined patterns is determined according to said unit vector.3. The apparatus according to said claim 1, wherein said calculatingdevice executes pattern matching between image data of a movingdestination and said predetermined pattern at said destination of saidpredetermined pattern.
 4. The apparatus according to claim 3, whereinsaid calculating device sets a detection estimating area in apredetermined range of which center is assumed to be separated by aninteger multiple of said unit vector; and wherein said calculatingdevice executes pattern matching between image data in said detectionestimating area and said predetermined pattern.
 5. The apparatusaccording to claim 1, wherein said image data and said unit vector aredisplayed in layers on said displaying means.
 6. The apparatus accordingto claim 5, wherein an additional line that is an extended line of saidunit vector and said image data are displayed in layers on saiddisplaying means.
 7. The apparatus according to claim 1, wherein saidspecimen is a semiconductor specimen on which a circuit pattern orwiring pattern is formed; and wherein said apparatus includes a CADsystem for storing layout data used to specify said starting point andan address of said ending point according to said circuit or wiringpattern design data.
 8. The apparatus according to claim 4, wherein saidcalculating device calculates the number of patterns when there is nopattern matching with said predetermined pattern in said detectionestimating area, as well as the number of patterns when there is apattern matching with said predetermined pattern.
 9. The apparatusaccording to claim 4, wherein said calculating device counts the numberof patterns when there is a pattern matching with said predeterminedpattern in said detection estimating area.
 10. The apparatus accordingto claim 9, wherein said apparatus further includes storage means forstoring a threshold value used to determine whether to determine thenumber of said patterns is proper or not; and wherein said calculatingdevice, when the number of said patterns does not satisfy said thresholdvalue, estimates the reason.
 11. The apparatus according to claim 9,wherein said counting device, when the number of said predeterminedpatterns does not satisfy said threshold value, displays a request forresetting the conditions for counting the number of said appearedpredetermined patterns on said displaying means.
 12. The apparatusaccording to claim 10, wherein said counting device estimates saidreason according to a distribution of the number of said appearedpredetermined patterns in an area that does not satisfy a condition “acase in which there is a pattern matching with said predeterminedpattern in a detection estimating area” with respect to a starting pointof cell counting in said area.